# 8 5v relay power

hi i bought this item from ebay http://www.ebay.com/itm/171027362353?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 and was curious on how to power it. is it just as simple as plugging a 9v power supply into it or do i need to add resistors? i am abit skeptical to be honest because i have never power this many relays before....any advice? im planning to make wire up my home thats why i need so many relays

They don't say how much current the relays need so the first step is to find the relay specifications:

http://www.songle.com/en/pdf/20084141716341001.pdf

The "L" in SRC-05-SL-C means 0.36 Watts. Since Watts is Volts times Amps we can divide by Volts to get Amps:

0.36 / 5 = 0.072 = 72 mA per coil. * 8 = 575 mA

That means you CAN'T power all 8 relays from an Arduino if the Arduino is running off USB power (500 mA). If the Arduino is running off a 7-12V power supply you should be able to use the Arduino 5V power to activate the relays.

Hi, Yes, John has the current issue well covered.

hi, but does it mean that if i use a dc power supply of 9v to my arduino, i dont need an external power source ?

Hi, You WILL need a separate 5V supply for the relay board. It draws too much current to run from the voltage regulator on the Arduino.

UNLESS you will only ever activate one relay at a time. But not a good idea.

Just a low-cost wall-wart type supply would be OK, such as http://yourduino.com/sunshop2/index.php?l=product_detail&p=123

DISCLAIMER: Mentioned stuff from my own shop...

cool! thanks very much! thanks for the advice

terryking228: You WILL need a separate 5V supply for the relay board. It draws too much current to run from the voltage regulator on the Arduino.

Since the eight relays, together, draw 575 mA when activated and the 5V regulaor on the Arduino UNO is capable of about 1000 mA I think the relay board would be able to work off the Arduino 5V pin if the Arduino is running off a 9V power brick of, say, 800 mA or more. I think the way to do it is to jumper vcc and Rvcc.

so if each relay requires approximately 75 mA, a power supply of 1A from a DC power supply should be sufficient right? but wouldnt the resistance be very high?

Hmmm....

The ArduinoInfo.Info WIKI (OK, Which I write !) says: (See http://arduino-info.wikispaces.com/QuickRef )

---------------------( COPY )--------------------- Power Considerations: The power pins are as follows:

VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). This is connected to the center terminal of the Coaxial "Power" connector. You can supply a voltage through this pin, or, if supplying voltage via the power connector, access it through this pin.

5V.The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN/Power Connctor via an on-board regulator, or be supplied by USB or another regulated 5V supply.

LIMITATIONS: If an external power supply is connected to VIN, the current available from 5V depends on the power dissipated in the onboard regulator, which is a maximum of about 1.5W. At 7V VIN this is about 700mA, at 9V VIN it's about 350 mA , at 12V it's about 200 mA.

Calculate: (VIN - 5) / 1.5

PRACTICAL LIMITS: The ATMEGA328 and other chips use about 120mA, so what's LEFT for your LED's , and other external devices is the limitations above minus about 150 mA, so now at:

VIN of: 7V it's about 550mA, 9V about 200 mA, and 12V 50 mA. -----------------( END COPY )----------------------

See detailed discussion here: http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html (Scroll to "Powering An Arduino")

So, at 9V on Vin 8 relays would be too much. At 7V in (If you can find a good 7V power supply) it's just marginal.

I still think the easy solution (which also allows total optical isolation) is a separate 5V 1A power supply for the relays.

Hmm.....

thank you for that very detailed description. i understand better now… 9v will be over kill! ill power it up using 6.5 v 1A power supply! one more question regarding the relay board. on the board, there is a vcc, rvcc and Gnd… what does it do ?

Hi, On the ArduinoInfo.Info WIKI HERE: See the Arduino Power section.

Relay Board details (even though you bought a similar one elsewhere) are explained here: http://yourduino.com/sunshop2/index.php?l=product_detail&p=156

hello,

I hope nobody minds for using this thread but I was wondering the same thing but in regards to the other 8 channel model currently being sold.

the model is this but 5V: http://www.hobbytronics.co.uk/8-channel-relay-board

the pins are different than the relay in the tutorial, they are:

-VCC -GND -IN 1-8 -COM -GND * the last two are connected with a jumper*

In the tutorial it says "If you isolate Arduino, you need to connect +5V ONLY (NOT GND) from Arduino to the VCC pin. The Arduino output pins go to IN1 through IN8. And again, these pins are Active LOW."

This model must be Active HIGH, because when writing a sketch or using the button example the relays turn on like any normal LED would without modding the sketch. So what I was wondering (and guessing) is, is instead of +5V from the arduino to the VCC pin like above I would connect GND from the arduino? Also should the external power supply be connected to GND or COM?

thanks for the info!

again my apologies for jumping in like this ;)

This model must be Active HIGH, because when writing a sketch or using the button example the relays turn on like any normal LED would without modding the sketch. So what I was wondering (and guessing) is, is instead of +5V from the arduino to the VCC pin like above I would connect GND from the arduino? Also should the external power supply be connected to GND or COM?

Yes that looks right. External 12V power should go to Vcc and Gnd The input signal goes from Signal Inputs to Com. Arduino Ground goes to Com. The jumper can be removed if you want the Arduino Ground to be separate from the 12V Ground.

again my apologies for jumping in like this

No Problem, Mai Wen Ti, we are all trying to jump to the right conclusions about all this stuff!

terryking228:
Hi, Yes, John has the current issue well covered.

Hi T

terryking228:
Hi, Yes, John has the current issue well covered.

Hi, sorry to resurrect an old thread, i see there are two vcc and two gnd (in each 8 pin and 3 pin group) , so I wonder if i connect external 5v to jd vcc i assume i connect the corresponding external gnd to the gnd in 3 pin group ?

And the VCC from arduino to the VCC in the 8 pin group or the one next to JD-VCC ?

Thanks before.

yes I too am interested in this since I plan to run 60 of these relays(8 of these boards) on a mega.

johnwasser linked to a page that details a stand alone relay but these banks have transistors and other circuitry outside of the relays.

in the ad linked in the OP it states "Each one needs 15-20mA Driver Current." and the one linked to in whiskeys post states "Each relay consumes approx 30mA when switched on (at 12V)"

so can I run that many of these?

Hutkikz: yes I too am interested in this since I plan to run 60 of these relays(8 of these boards) on a mega.

in the ad linked in the OP it states "Each one needs 15-20mA Driver Current." and the one linked to in whiskeys post states "Each relay consumes approx 30mA when switched on (at 12V)"

Since when do you believe adds... Most 8-relay boards listed on ebay etc. have optos between Arduino and relay. The boards with an opto/red LED/1k resistor draw 2mA per relay from the Arduino pin.

60 relays is a lot. Even for a Mega. You might have to look into e.g. a two wire I2C expander. What are you planning to control. There might be easier ways of doing things. Leo..

12v lights

http://forum.arduino.cc/index.php?topic=321511.0

12volt lights.

What type of lights. LED or incandescent. Standard or halogen.

Depending on this, it might be better to use an Adafruit PCA9685 breakout board (16 channels). Four of those boards can be fully controlled, and even PWM dimmed, with four wires. Two for the data, and two for the supply. Expansion to ~60 boards is possible... An UNO will do if the code fits. Depending on the lights, you need LED drivers or logic mosfets. Leo..

not sure whose questions are being asked as it seems that this thread has been hi-jacked at least twice…

what some people cannot grasp is that the relay board as 3 distinct and separate power needs.

the RELAY details what it, and it alone requires for power. you absolutely must provide that power to the relay input power connector.

the CONTACTS or outputs have to be anything, the only requirement is that the voltage has to be between the ratings for the relay contact power the relay data sheet. 230 volts AC is often the max, but each relay is listed.

also you have to know if your load is restive or inductive. a light or a motor… the data sheet will list separate ratings for the application.

now the part that offers the most confusion. the ground common between the relay and the Arduino.
not sure why, but many of these boards have and require a common connection for grounds. for the most part, there is no need and no problem with connecting the grounds. it is common practice too have all the grounds tied together. if you absolutely cannot live with the grounds tied together, you must isolate the ground of the opto’s so you can use them as true isolators.

if the board is wired to use the ground as part of the logic circuit, you may have to connect grounds or get another board.

lastly the opto’s. if you were to use the data sheet of the coil and determine load, then use the data sheet of the opto and determine the power needed to saturate FOR THAT LOAD, in almost all cases, 10mA will drive the opto into saturation for the coil load. be advised that the coil has two loads, the initial load to create the magnetic field that pulls in the contacts and the load to maintain that field. the initial load is two to three times higher than the sustained load.

if you are driving more than a few of these, then a shift register might be in order. it eliminates a lot of the problems with power for the opto’s.

bottom line is that you will be required to offer power supplies.
one for the relay coils. one for the logic for hte opto’s, one for the Arduino and it’s circuits and another for the load side of the coil.

if you offer one massive 5 volt power supply, you can power all the relays and the opto’s and the arduino.
you might want to add some filtering on the relay side of that, but nothing too fancy.

Hutkikz:
yes I too am interested in this since I plan to run 60 of these relays(8 of these boards) on a mega.

johnwasser linked to a page that details a stand alone relay but these banks have transistors and other circuitry outside of the relays.

in the ad linked in the OP it states “Each one needs 15-20mA Driver Current.”
and the one linked to in whiskeys post states “Each relay consumes approx 30mA when switched on (at 12V)”

so can I run that many of these?

What I gather from searches is you will need an external power supply to power more than 4 relays in that board.

I got my answer after searching harder, this post below answers my question how to wire external 5V 1A adapter to the 8-channel board.

Arduino VCC goes to 8pin’s VCC
External +5V goes to JD-VCC
External GND goes to 3 pin’s GND
8pin’s GND is not used for complete opto insulation.